1. Field of the Invention
The present invention relates to a design and method of manufacturing a surgical suturing needle that can be used generally for adjoining or closing adjacent portions of skin or tissue. More particularly, the suturing needle design and manufacturing process of the present invention are directed to a new class of suturing needle particularly suitable in plastic and reconstructive suturing applications.
2. Description of the Prior Art
Suturing needles for applying sutures, or stitches, by hand in cutaneous and subcutaneous tissues are well known in the art. The sutures are typically used to close wounds or adjoin adjacent tissue, often at the conclusion of a surgical procedure. Conventional suturing needles are usually made from a cut blank of material such as stainless steel. The cut blank is metal-worked using well known machining techniques to form a surgical suturing needle. The needle generally includes a shaft, a rear end portion with means to grip or secure a suturing thread and a needle head at a front end portion for puncturing skin and tissue through which the needle travels. The needle head typically includes a sharpened needle tip at its distal end and cutting edges.
Needle sharpness is an important consideration in designing and manufacturing surgical suturing needles. Sharper needles require less force to penetrate the tissue and thus cause less tissue trauma. In addition, sharper needles reduce fatigue on the needle itself, making it less likely to bend or break during suturing. Needle sharpness is typically defined in terms of a so-called penetration force -- the force necessary for a needle point to puncture, or penetrate, the tissue. The penetration force is primarily determined by the design and sharpness of the needle point. However, needle sharpness is also affected by a drag force of the needle as it travels through the tissue. The ability of the needle to pass smoothly through the tissue is a desirable characteristic. The drag force of the needle depends upon the design and sharpness of the needle, especially the needle head. The quality of a lubricating coating on the needle also affects the drag force. For example, if the lubricating coating on the needle wears off, the drag force on the needle increases with each pass of the needle through the tissue. This effect could give the surgeon-user the false impression that the needle is failing to retain its sharpness.
Another important consideration in designing and manufacturing surgical suturing needles is their resistance to bending or breaking during use. The strength of a suturing needle is a measure of its ability to resist bending and is determined by such factors as (a) the material selected to make the needle, (b) the cross-sectional shape of the needle, and (c) the heat treatment process received by the needle during manufacturing. However, needle strength should be balanced by needle ductility, which is defined in terms of the ability of the needle to be reshaped after it flexes from its original shape. A surgical needle with good strength characteristics but having little or no ductility can be brittle and may snap and break during use. In use, the surgical needle is held at its rear end by a needle holder and the needle tip is forced against the tissue to be sutured. This action creates a bending moment on the needle body, and a needle with some degree of ductility will be able to be reshaped to its original shape without breaking. It is generally known that in working with a metallic material, as the strength of the material increases the ductility will decrease. Therefore, it is desirable to carefully balance the strength and ductility characteristics of a suturing needle.
Another desirable attribute is stability of the suturing needle in a needle holder. The needle holder is typically used to grip and stabilize the needle as it passes through the tissue.
The subject invention provides significant advances over conventional surgical suturing needles by improving needle attributes such as needle sharpness and resistance to bending or breaking during use as well as other desirable attributes.